THE COORDINATION BEHAVIOR OF THE SQUARATE ANION IN RHODIUM(I) CHEMISTRY

Preparation of the neutral [Rh-2(mu-sq)(COD)(2)] (1) (sq=squarate) and ionic [Rh(phen)(COD)][Rh(sq)(COD)] (2) and [Rh(dppe)(2)](2)[sq] (3) c omplexes is reported. Complex [Rh-2(mu-sq)(CNR)(4)] (4) (R=p-tosylmeth ylisocyanide) has been prepared by substitution of the diolefinic liga nds of complex 1. Carbonylation of compounds 1 and 2 gave [Rh-2(mu-sq) (CO)(4)] (5) and [Rh(phen)(CO)(2)][Rh(sq)(CO)(2)] (6), respectively. C ompound [Rh-2(mu-sq)(CO)(2)(PPh3)(2)] (7) was prepared by addition of PPh3 to complex 5. Complex 7 undergoes oxidative addition of molecular iodine leading to the rhodium(III) compound [Rh-2(mu-sq)I-4(CO)(2)(PP h3)(2)] (8).